Linux, OS X, XP - Looking for expert opinions.

I hate to have my first post be a new thread, but rest assured I have used the search feature and read lots of threads before posting!

Here is my situation. I'm in the market for a new computer for work. I am a Web designer/developer/programmer/analysist/master. Yes, I do everything from graphics to server administration. I am a huge open source fan, and have been running a sucession of Linux flavors along side Windows 2003 Server on my home computer. I consider myself an expert computer user and can figure out just about anything.

Here is a short list of what I currenetly use for what.

Linux:

Most Programming & Developing

Server Setup/Testing

Every day use

Windows

Photoshop (would change if I have OSX)

System Design (M$ Viseo & other tools)

IE 6 & 7 Testing

Some Programming - Not huge requirement

Instant Rails for when I am feeling lazy

Other random Windows only Aps

I grew up on Macs, matured on Windows, and fell in love with the open source community and linux.

If left up to me I would probibly stick with this kind of a set up. But my boss is a huge mac fan and is heavily pushing a mac. And, being the OS fan I am, I think three is better then two!

So now after all that background here is my question:
Is it possible to have the best of three worlds? I would be running dual monitors on a MacPro. I need everything to work on every OS.

What is the best way to do this?
Dual boot OSX & Linux then run Windows as a parallel?